Method of making rolls



Jan; 16, 1940. F. c. T. DANIELS' 2,187,415

METHOD OF MAKING ROLLS Filed May 13, 1939 A\\. 'll/111111111111111INVENTOR mold; in the mold to percolate upward through the unsolidiedportion of the initial body of metal to mix homogeneously therewith. The-rate at which the inoculant metal is added I make so slow that there isno bodily displacement of any portion of the metal initially containedin the mold, but on the contrary as the level of the total metal in themold slowly rises, the softer inoculant metal ,with great rapidityspreads through the body of initial metal, the concentration of thesofter metal, rather than its distribution, becoming greater as theinoculation slowly proceeds. It is thus the inoculated metal, and notthe initial hard metal, which rises to flll the mold cavity for theupper roll neck.

As inoculation proceeds, and the total volume of metal in the moldincreases, the level of the metal rises upwardly beyond the upper moldspace for one of the roll necks, and into the adjacent hot top of themold. By appropriate proportioning of the total mold cavity and thelevel (about the body cavity of the mold) to which the mold initially isfilled, I may add inoculant metal in a proportion of from 15% to 25% thetotal weight of the roll without displacing any metal from the mold.

The slow addition of the inoculant metal is a feature of my method whichshould be emphasized since. such slow addition results in homogeneity inthe composition of the metal in al1 regions of the roll, save thechilled surface of the body. This is resultant from the fact that thequiet inoculation renders it possible to avoid any such thrust of theinoculant metal as bodily to displace any of the still liquid metalalready contained in the mold. This is in accordance with my discovery,above noted, that inoculation seems to proceed so rapidly throughout thebody of initial metal in the mold that is stillin the liquid state(i.,e., that metal that has not been congealed by the bodyvchill mold).I have found that, depending upon the conditions of the rollcastingoperation, I may vary the time of pouring the inoculant from 4 to 20minutes; but in any case it is added slowly, and either continuously orin very small closely timed increments.

It will be readily understood that my method of quiet inoculation avoidsall the disadvantageous effects incident to relatively violentdisplacement of metal from the mold. By heat transfer through the bodyof metal in the mold, it tends to preserve uniformity of temperature inthe entire metal of the casting, and ter/ids wholly to eliminate gasesfrom the metal during the relatively extended period in which theinoculant metal is added. Tests have shown the rapidity with which thetmetal in the upper region of the mold becomes uniform in compositionwith that in the lower mold regions, and that the progress of.inoculation after the first introduction of the `inoculant metalconsists chiefly in progressive concentration 'of the inoculant. This isshown by the approximately complete homogeneity in character of themetal in the necks and body interior of each inoculated roll.

` The method of ,my invention provides a practical process for makingrollsfin which it is desired to combine strengthwith a desirably highsurface hardness and hardness penetration. I have found that theadvantages of my method of roll casting are realized in the casting ofmetalworking rolls up to an 85 scleroscope hardness and with a chilleddepth in the approximate proportion of from 1 to 2 inches for a 12 to 18inch diameter roll, and of from 2 to 4 inches for a 20 given as follows:

3. 28 3. 20 3. 46 51 95 96 24 46 43 4. 2l 1. 04 4. 49 32 68 96 l. 95 M026 45 In each formula the percentages of alloying ingredients are given,as is usual, by weight, and in each the remainder of the composition isiron,

except for small quantities of the usual impurities.

In practicing my method it is advantageous that the hard, initiallycast, metal should be one of those ferrous compositions, or alloys,which do not tend rapidly to thicken when poured into the mold. Thepropriety of utilizing an initial metalwhich tends to retain fluiditywill be clear in view of the manner in which I perform the inoculationstepgadding the inoculant metal slowly, and avoiding bodily displacementof any substantial portion of the initial metal. If the initial metal beof a sort which tends rapidly to thicken, inoculant may in substantialquantity be nonetheless added. The proportion of inoc ulant which mayhomogeneously be distributed through the body of metal initially in themold is, however, limited by the decreased time available for theinoculation due to obstruction to its spreading presented by thethickening of the metal initially in the mold.

Usually it is desirable that the softer inoculant metal be of suchcomposition that it develops to a great extent a graphitizing tendency,so that it may serve adequately to soften and strengthenI the initiallyhard metal which it inoculates. A generally advantageous formula for theinoculant metal maybe given as follows:

Formula No. 1

The remainder iron and small quantities of the 5 usual impurities.

Formula No. 2

Per cent Carbon 4.00 Silicon 2.10 Manganese 1.00

The remainder iron and small quantities of vthe usual impurities.

In connection with the duration of the period of quiet inoculation,given above as from about 4 to about 20 minutes, I prefer to employ asmuch time in inoculation as the teeming temperature and composition ofthe metals will permit. Thus, if the initially cast metal be teemed athigh temperature, and be of a composition capable of retaining acondition of high iuidity for a rela.- tively long time (the inoculantmetal similarly meeting those requirements) I prefer to teem so slowlythat as much as ten minutes is usually taken for conducting the quietinoculation step, in making rolls of average size. If on the contrarythe conditions are such that a lesser order of fluidity of the initialmetal is to be expected, the time during which the inoculant is addedshould be shortened.

In relating the time during which the inoculant metal is added to thesize of the roll which is cast by my quiet inoculation method, and therelative proportions of the metals desirably poured in the severalstages of casting, I give the following illustrative information. A rollrequiring 10,000 lbs. of total metal, I have cast with 7500 lbs. ofmetal in the initial pouring, and have then inoculated it with 2500 lbs.of the inoculant metal, taking about minutes :for the inoculation step.I have cast a 30,000 lb. roll, using 21,000 lbs. of metal in the initialpouring, and adding 9000 lbs. of the inoculant metal during aninoculation period of minutes. I have cast a 71,000 lb. roll, using40,000 lbs. of metal during an inoculation period of about 10 minutes.The roll last noted represents approximately the maxiniurn weight oirolls commonly cast. It is to be understood, however, that if evenheavier rolls are being cast, the inoculation period may well beextended beyond minutes. In each noted instance the initial metal waspoured at a temperature in the neighborhood of 2500" F. and theinoculant was poured at a temperature `in the neighborhood of 2400" Ii.

In general I may say that I prefer to inoculate as slowly as the severalconditions oi the casting process will permit; and in this connectionmay note that (other conditions being equal) it is possible, anddesirable, to inoculate a large roll casting proportionally more slowlythan a small roll casting, because of the greater total heat content ofthe larger body of metal. One skilled in the art of roll casting will,with these general guides, be enabled, without experiment, and usingmerely reasonable care, properly to time the length oi the inoculationperiod. Y

hy the simple method above described, I have made rolls having in theroll body a scleroscope i hardness of from 00 to 85; and in which testpieces taken from the necks, and the interior of the roll body show(uniformly for each individual roll) a tensile strength of from 32,000lbs. per su. in. to 40,000 lbs. per sq. in.

It has .been indicated above that nay/quiet inoculation methodNis notlimited to procedure which provides a definite, or clean chillstructure. Illustration of that fact is given in the formulae for theinitially poured metal of the roll. Of these formulae, 1, 2, and 3 givea substantial depth of deiinite, or clear chill structure, whileformulae 4 and 5 give a roll having a hardened surface, but without asharply dehned, or clear chillstructure. These latter rolls are,therefore, to be considered .to be of the grain type, rather than of thechilled type.

It may be that an initial metal which, because oi its chill, will have asuiilcientiy hard surface,

. may, because of its composition and the slow rate of cooling in thesand portions of the mold, give necks which, although they contain arelatively high proportion of graphite, have their graphite in largeplatey structure, and are for that reason weak. In such case aninoculant metal though it be inherently "harder than the unchiiledportion of the initial metal, may so improve the form and distributionof the graphite structures in the necks, so to increase the strength ofthe necks. Whereas 'throughout the specification the initial .metal hasbeen spoken of as hard metal, and the inoculant metal as soft metal (asis usually the case) it is thus apparent that the procedure of my methodis consistent with the use of an inoculant inherently no softer than theinitial metal. It must, however, be of strengthincreasing character.Thus the inoculant metal will have strength-increasing qualities, thoughnot necessarily softer but. even harder than the initial metal, if it bewithin 'the ranges of the commonly known high-test cast irons. Aproportioning of alloys in the initial metal and the inoculant also maycause the inoculant to impart the desired strengthening effect withoutbeing inherently softer than the initial metal.

I claim as my invention:

1. In making cast-iron rolls having a hardened body surface andrelatively soft and strong body and necks those steps which consist ininitially iilling a mold contoured for the casting of rol1s\ to a levelslightly above the body cavity of the mold, surface chilling the bodyportion of the roll to form a cylindrical shell of solidified metal, andinoculating all the initial metal of the roll other than that containedin the chilled surface of the roll body by slowly introducing at thebottom of the mold a strength-increasing different metal whilepermitting the level of the total metal to rise in the mold.

2. In making cast-iron rolls having a hardened body surface andrelatively soft and strong body and necks those steps which consist ininitially hlling a mold contoured for the casting of rolls to a levelslightly above the central body cavity ci the mold with a metal ofrelatively high iiuidity, surface chilling the body portion of the rollto form' a cylindrical shell of solidied metal, and during thecontinuance of the fluidity of the said metal initially in the moldinoculating all the said initial metal of the roll other than that inthe chilled surface of the roll body by slowly and quietly introducingat the bottom of the mold an inoculant strength-increasing metaldifferent from the initial metal, while permitting the level ofthe totalmetal to rise in the mold.

3. In making cast-iron rolls having a hardened body surface andrelatively soft and strong body and necks those steps which consist ininitially filling a mold contoured for the casting of rolls to aAlevelslightly above the central cavity of the mold, surface chilling the bodyportion of the roll to form a cylindrical shell of solidified metal, andquietly inoculating substantially the entire body of the metal initiallyin the mold other than that contained in the chilled surface of the rollbody by adding as slowly as the per- .sistence of fluidity in the saidinitial metal will permit strength-increasing dierent inoculant metalintroduced at the bottom of the mold, while permitting the level of thetotal metal in the mold to rise.

4. In making cast-iron rolls having a hardened body surface andrelatively soft and strong body and necks those steps which consist ininitially filling a mold contoured for the casting of rolls 'to a levelslightly above the central body cavity of the mold, surface chilling thebody' portion of the roll to form a cylindrical shell of solidied metal,and effecting quiet inoculation of all the initial roll metal other thanthat comprised in the chilled surface of the roll body by slowlyintroduoing at the bottom of the mold an inoculant metal softer thanthat rst introduced into the mold, while permitting the level of thetotal metal to rise in the mold.

5. In` making composite cast-iron rolls having a hardened body surfaceof one composition and a body interior and necks of a different composi.tion the steps of pouring into a mold contoured for the casting of rollsmetal to be included in the hardened body surface of the roll to a levelabove the body cavity in the mold, forming a solidified shell on thebody region of the initially 6. In making composite cast-iron rollshaving a hardened body surface and a body interior and necks of a softerand stronger composition than that included in the hardened body surfaceof the roll, the steps of pouring into a mold contoured for the castingof rolls metal to be included in the hardened body surface of the rollto a level above the body cavity in the mold, forming a solidied shellon the body portion of the initially poured metal in the body cavity ofthe mold, then while retaining in the mold substantially the totalinitially poured metal mixing a molten strength-increasing and softeningmetal with the still-liquid portion of the total initially poured metalstanding in the mold.

FRED C. DANIELS.

